Antenna structure and wireless communication apparatus including same

Abstract

In an antenna structure in which a base is mounted in a ground region on a circuit board, the base having formed thereon a driven radiating electrode and a parasitic radiating electrode, the parasitic radiating electrode causing multiple resonance at least in a harmonic resonant frequency band of the driven radiating electrode, capacitance loading means for loading a capacitance to a harmonic-mode zero voltage region of the driven radiating electrode is provided. The capacitance loading means is electrically connected to a ground electrode in the ground region on the circuit board via a grounding conduction path and switching means. By switching the switching means ON / OFF, capacitance loading by the capacitance loading means to the harmonic-mode zero voltage region of the driven radiating electrode is switched ON / OFF to switch a base resonant frequency in a base resonant frequency band of the driven radiating electrode.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This is a continuation under 35 U.S.C. §111(a) of PCT / JP2006 / 323818 filed Nov. 29, 2006, and claims priority of JP2006-036830 filed Feb. 14, 2006, both incorporated by reference.BACKGROUND[0002]1. Technical Field[0003]The present invention relates to antenna structures provided in wireless communication apparatuses, such as cellular phones, and to wireless communication apparatuses including the antenna structures.[0004]2. Background Art[0005]FIG. 13a is a schematic perspective view showing an example of an antenna structure (e.g., refer to Patent Document 1). The antenna structure 40 includes a dielectric base 41 having a rectangular parallelepiped shape, and a ground electrode 42 is formed on the bottom surface of the dielectric base 41. Furthermore, on the top surface of the dielectric base 41, a driven radiating or feeding electrode 43 and a parasitic radiating or non-feeding electrode 44 are provided adjacent to each other, separated...

AI Technical Summary

Benefits of technology

[0027]As described herein, a base in an antenna structure has formed thereon a driven radiating electrode and a parasitic radiating electrode, and the parasitic radiating electrode is configured to cause multiple resonance with the driven radiating electrode by performing an antenna operation at least in a harmonic resonant frequency band of the driven radiating electrode. The multiple resonance by the parasitic radiating electrode in the harmonic resonant frequency band of the driven radiating electrode serves to increase the bandwidth in the harmonic resonant frequency band of the driven radiating electrode.

[0028]Furthermore, capacitance loading means for loading a capacitance to a harmonic-mode zero-voltage region of the driven radiating electrode, a grounding conduction path that electrically connects the capacitance loading means with the ground electrode on the circuit board, and switching means, provided in the grounding conduction path, for switching ON / OFF of conduction between the capacitance loading means and the ground electrode are provided. When the switching means is ON, the capacitance loading means is grounded to the ground electrode, so that the capacitance loading means loads a capacitance formed between the harmonic-mode zero-voltage region of the driven radiating electrode and the ground to the harmonic-mode zero-voltage region of the driven radiating electrode (capacitance loading is ON). Thus, compared with a state where the switching means is OFF so that the capacitance is not loaded to the driven radiating electrode (capacitance loading is OFF), when capacitance loading is ON, the electrical length of the driven radiating electrode increases in accordance with the magnitude of the loaded capacitance, whereby the base resonant frequency of the driven radiating electrode is switched to become lower. The switching of the base resonant frequency of the driven radiating electrode serves to increase the bandwidth of the base resonant frequency band of the driven radiating electrode.

[0030]That is, in the configuration, since the bandwidth of the harmonic resonant frequency band of the driven radiating electrode increases by multiple resonance with the parasitic radiating electrode so that it is possible to achieve a desired frequency band, it is desired that the harmonic resonant frequency band of the driven radiating electrode does not change. Taking this into consideration, without changing the harmonic resonant frequency band of the driven radiating electrode, by switching only the base resonant frequency of the driven radiating electrode through switching of the ON / OFF of capacitance loading by the capacitance loading means, it is possible to increase the base resonant frequency band of the driven radiating electrode.

[0032]Furthermore, the driven radiating electrode has such a form that the feeding end and the open end thereof are provided adjacent to each other with a space therebetween, and a current path between the feeding end and the open end has a loop shape. Thus, advantageously, it becomes readily possible to adjust the base resonant frequency and the harmonic resonant frequency of the driven radiating electrode. That is, since the driven radiating electrode has such a form that the feeding end and the open end thereof are provided adjacent to each other with a space and a current path between the feeding end and the open end has a loop shape, a capacitor is formed between the feeding end and the open end. This capacitor contributes more to the harmonic resonant frequency than to the base resonant frequency. Therefore, with the capacitor between the feeding end and the open end, it is possible to adjust the harmonic resonant frequency of the driven radiating electrode without substantially changing the base resonant frequency. That is, for example, by setting the electrical length between the feeding end and the open end of the driven radiating electrode to be such an electrical length that a predetermined base resonant frequency is achieved, and setting the capacitor between the feeding end and the open end to have a such a magnitude that a predetermined harmonic resonant frequency is achieved, it is possible to adjust the base resonant frequency and the harmonic resonant frequency independently of each other. Thus, it becomes readily possible to set both the base resonant frequency and the harmonic resonant frequency of the driven radiating electrode individually to predetermined frequencies.

[0033]Furthermore, since the driven radiating electrode has such a shape that the current path between the feeding end and the open end has a loop shape, it is possible to increase the electrical length of the driven radiating electrode without increasing the size of the driven radiating electrode. Thus, it is possible to reduce the size of the base, i.e., to reduce the size of the antenna structure.

Problems solved by technology

Even with the antenna structure 40 having an increased bandwidth as described above, it has been difficult to satisfy the demand for multiple bands due to the insufficiency of frequency bands that can be used for wireless communication.

Images